This invention relates to an electronic device, such as a negative-characteristic thermistor, having lead terminals with the outer surfaces coated with a resin material for improved mechanical strength.
Electronic devices of the kind having an electronic element covered with a resin material or the like for protection against the external environment have been widely in use. In the case of a device with lead terminals, the terminals, too, are sometimes covered for improving electrical insulation. For covering a lead terminal longitudinally, a material having a silicone rubber resin as its principal component may be used to coat it from outside, or the lead terminal may be inserted into a preliminarily formed tube made, for example, of cross-linked polyolefin.
Prior art lead terminals which are thus coated, however, have had problems of various types. In the case of a lead terminal covered with a silicone rubber type resin material, the coating film is easily damaged or peeled off when an external force such as a scratching force is applied on the lead terminal during its fabrication process, whether it is done by a machine or manually. In the case of a lead terminal covered with a preliminarily formed tube, the cost of manufacturing the tube is considerable, and the production involves an extra process of inserting the terminal into the tube. In addition, an uncovered gap may be left between the externally covered main body of the electronic element and the lead terminal covered with a tube such that the electrical insulation of the device may be compromised.